Track lighting systems are well known whereby a lighting fixture is slidable along a track adapted to be mounted on a ceiling or some other supporting surface. The track is generally channel-shaped and typically is in the form of an extrusion made of aluminum or some other suitable metal or metal alloy. One or more lighting fixtures may be slidable along the track so that the positioning of the lighting fixtures can be adjusted as desired. Electrical power is generally supplied to the adjustable lighting fixtures by at least two electrical conductors in the form of wires or bus bars supported by an insulator mounted in the track. Typically, the insulator is also channel-shaped and is securely mounted within the channel-shaped track. The insulator is generally made of a polymeric resinous plastic material.
Each of the lighting fixtures typically includes an adapter which is slidable along the track. A supporting member extends downwardly from the adapter for supporting a lamp housing which contains a lamp socket for receiving a lamp. The adapter typically includes a pair of electrically conductive contacts which are slidable along the bus bars and are connected by means of wire leads to the lamp socket.
Underwriters Laboratories has established electrical safety standards which regulate, among other things, the minimum spacing between each of the electrical bus bars and the adjacent portions of the metal track. The purpose of the minimum spacing is to obviate or minimize the possibility that one of the bus bars may come into contact with the metal track. Any such contact may produce an electrical shock hazard, if the track is not grounded, or a short circuit hazard, if the track is grounded.
For a long time, the minimum spacing required by Underwriters Laboratories was 1/32 of an inch between any bus bar and the metal track, whether separated from the bus bar by air or insulating material. A great many track lighting systems have been manufactured and installed, utilizing this minimum spacing of 1/32 of an inch, which in many instances was established by interposing a corresponding thickness of the insulator between the bus bar and the track.
In recent times, Underwriters Laboratories has modified its electrical safety standards so as to increase the minimum spacing from 1/32 of an inch to 1/16 of an inch. The necessity of compliance with this increased thickness requirement has created a need for producing improved track and insulator constructions which achieve the increased spacing between each bus bar and the track, without changing the spacing between the bus bars and without significantly changing the external and internal dimensions of the mechanical components of the track, so that the improved track and insulator constructions will be completely compatible with the previous track and insulator constructions whereby all existing lighting fixtures can be mounted for sliding adjustment along the improved tracks and insulators, and whereby existing connectors and other accessories can be used with the improved track and insulator constructions, with full compatibility and without any need for modifying the accessories.